Recently, the cost of low power induction heating or IH systems (0.01 to 3 KW) has fallen due to advances in semiconductor power switching technology, enabling various commercial and consumer heating applications. Induction heating has the ability to heat metallic or other electrically conductive objects with no wires or other physical contact, as has been advantageously done for years in such applications such as induction cooking.
Another more recent innovation, Radio Frequency Identification or RFID systems, provides remote identification of vehicles on tollways for billing purposes, and identification of palletized items in warehouses so that inventory counting can be easily accomplished. RFID systems fall broadly into several categories such as short range (a few inches usually) or long range (up to many meters), passive (the RF field from the reader or interrogator powers the “tag” on the object), active (containing a battery to power some data transmission mechanism means within the tag).
In addition, RFID systems can not only send out a unique code from Tag to Reader to identify the tagged article, but the Reader can modify the data within the tag to show, for example, that the tag has been read on such and such a date.
RFID tags can also absorb information from the environment in which they are used, such as temperature or humidity, salinity or even blood glucose levels. In this way the RFID system can form an important part of a feedback control loop to regulate such a variable.
One ubiquitous parameter that needs control is the degree of heating (temperature regulation) of materials for various purposes. As IH is a form of no contact or “wireless” electrical heating, RFID systems have cleverly been employed to wirelessly provide feedback as to the temperature of an inductively heated system. U.S. Pat. No. 3,742,178 teaches a system that controls temperature in a cooking vessel by a tag-like device built into a piece of cookware to regulate the temperature thereof, although the cookware is not “identified”, per se, by this simple system. More advanced systems as taught in U.S. Pat. Nos. 6,320,169 and 6,664,520, by Clothier, teach temperature control and many other product/system features heretofore unobtainable by use of modern RFID Tag/Reader systems in conjunction with induction heating systems.